The present inventor has successfully pioneered the dual mode preamplifier for electric guitar. His prior U.S. Pat. No. 4,211,893 (the disclosure of which is incorporated into this patent by reference) has heretofore come to define the state of the art, and has been embodied in a product line which has achieved significant commercial success and has since become recognized as a standard of excellence in the electric guitar amplifier field.
The dual mode amplifier described in the '893 patent offered a "solo enhancement" mode (i.e. the "lead" mode) which added massive amounts of carefully cultured harmonic distortion to simulate (and go beyond) the sounds produced by a power amplifier driven into extreme saturation clipping. The virtues of the '893 dual mode amplifier were several. First, although solo enhancement has as its origin the overdriven power section, the dual mode amplifier (being a preamplifier processing system rather than an overdriven power amplifier) was operable irrespective of playing output loudness. Second, the dual mode amplifier offered more control over tonal response and gain characteristics. And, third, it was presettable and could be easily switched between its solo and rhythm modes by footswitch action of the performer during live performances.
One drawback of the prior dual mode amplifier was its relative complexity and related expense, due to the particular arrangement and number of components required to form it. Thus, a hitherto unsolved need has arisen for an improved dual mode musical instrument preamplifier implemented with a streamlined circuit design which achieves superior results with fewer circuit elements and lower complexity and cost for implementation.